This invention relates to patterning touch fastener elements, and more particularly to self-engageable patterns of mushroom-type fastener elements.
Touch fasteners generally include those with male fastener elements, such as those shaped as mushrooms, palm trees or hooks, engageable with loop or fibrous elements or with complementary arrays or patterns of male fastener elements. Patterns of male fastener elements that are engageable with themselves, or with another fastener having a similar pattern, are called self-engageable. To be self-engageable, a fastener element pattern must have an arrangement of fastener elements that allow the heads of two identical such arrays to pass by one another, and then to engage one another with their overhanging portions. In order for the heads of the mating fasteners to pass one another during engagement, the overall percentage of the area of each fastener element array occupied by the footprints of the heads, or the head density as it is sometimes called, must be less than 50 percent. The ratio of individual inter-element engagements to the total number of fastener elements of one of the identical engaged arrays is the bulk engagement ratio. Because one fastener element may be simultaneously engaged with multiple fastener elements of another array, it is possible for bulk engagement ratios to exceed 100 percent. Typically, the stems of the fastener elements are flexible to allow the heads to pass by one another as the fastener arrays are brought into engagement.
In many previous patterns of fastener elements, the elements were arranged in straight, ordered rows, and very efficient methods are available for molding fastener element stems integrally with a base in straight rows, such as by continuous molding of stems and base on a rotating mold roll made up of stacked plates, many plates each providing the cavities for a respective row of fastener element stems, as disclosed in U.S. Pat. No. 4,794,028. After stem molding, the fastener element heads may be formed by heating the stem ends and then pressing against them with a chilled surface, as is shown in U.S. Pat. No. 6,248,276, or by otherwise flowing resin of the distal stem ends to form overhanging heads. While readily formed, many straight-row patterns tend to perform best for self-engagement at an engagement angle, the angle between the directions of extent of the rows of the engaged arrays, of zero degrees. For enabling engagement at a variety of other angles, it has been suggested that fastener elements should be arranged with a very low degree of order rather than in equally spaced, straight rows. While such unordered arrangements can provide for more uniform engagement rations over a wide variety of engagement angles, such that the mating arrays can be engaged without precise alignment, this typically comes at a reduction in the bulk engagement ratio at a zero degree engagement angle, the engagement orientation occurring most frequently in many fixed-position applications, and places some limitations on manufacturing method. Furthermore, with most unordered patterns there will be some degree of undesirable direct overlap of the stem positions of the engaging arrays in almost any engagement orientation, forcing the overlapped stems to buckle or significantly deflect laterally to complete engagement. The ratio of the number of overlapped stems to the overall number of fastener elements in one of the arrays is called the bulk overlap ratio.
Many straight row or otherwise highly ordered patterns allow the engaged arrays of fastener elements to move laterally with respect to each other, or slip. Gross slip can occur in the direction of the rows of some straight row patterns, or in incremental motions in multiple directions in other patterns.
Further improvements in the arrangement of fastener elements in self-engageable patterns are desired.
According to one aspect of the invention, a touch fastener product has a sheet-form base and an array of fastener elements, each fastener element having a stem extending from a broad side of the base to a distal head overhanging the base. The fastener elements are arranged in an ordered pattern of straight rows, with the heads of the fastener elements covering the base at a head density of between about 20 and 35 percent. The fastener elements are arranged to define a sufficient number and pattern of pockets between associated groups of adjacent stems to provide a bulk locking ratio of at least 10 percent when engaged with an identical pattern at a zero degree engagement angle. Preferably, the head density is between about 25 to 33 percent, or about 31 percent for some applications.
In some embodiments, the fastener elements are arranged to have a bulk engagement ratio, when engaged with an identical pattern at a zero degree engagement angle, of at least 100 percent, preferably at least 150 percent, and more preferably at least 200 percent.
In some cases, the bulk locking ratio is at least 20 percent, preferably at least 25 percent.
The fastener elements, for some applications, are advantageously arranged in a repeating pattern of row groupings, with each row grouping having a three row band of fastener elements spaced apart from adjacent rows of fastener elements by a distance greater than row spacing within the band. In some cases, the three row band consists of two outer rows of laterally aligned fastener elements and a middle row of fastener elements longitudinally offset from adjacent fastener elements of the outer rows. The middle row is preferably equidistant from two adjacent fastener elements of each of the outer rows.
In some configurations, a clearance between opposing surfaces of adjacent fastener element heads along the middle row is less than a nominal lateral extent, measured long the middle row, of the fastener element heads, such that during engagement, at least some of the fastener element stems of the middle row are deflected.
Preferably, particularly in such configurations, a clearance between opposing surfaces of adjacent fastener elements of the outer rows, measured across the three row band, is greater than a nominal lateral extent, measured long the middle row, of the fastener element heads, such that engagement does not require the deflection of both fastener elements of each opposing outer row pair.
In some patterns, each row grouping comprises the three row band and at least one single row band of fastener elements. For example, in one case, each row group consists of the three row band and a single row band of fastener elements spaced midway between the three row band of the grouping and a three row band of an adjacent grouping. In another illustrated pattern, each row group consists of the three row band and two single row bands of fastener elements separated by a distance greater than the row spacing within the three row band.
In some embodiments, the fastener elements are arranged in a repeating pattern of four-element clusters, with each cluster consisting of four fastener elements arranged at four corners of a four-sided polygonal area and spaced from adjacent clusters by a distance greater than a greatest side length of the polygonal area. The four-sided polygonal area may be rectangular, for example, or substantially square.
In some constructions, the fastener elements are arranged in a repeating pattern of four-element clusters, with each cluster consisting of four fastener elements arranged at four corners of a four-sided polygonal area. A clearance between a first pair of opposing fastener element heads at opposite corners of the area is greater than a nominal diameter of the fastener element heads, and a clearance between a second pair of opposing fastener element heads at opposite corners of the area is less than the nominal diameter of the fastener element heads.
For many touch fastener applications, the array should have an overall fastener element density of at least 200 fastener elements per square inch (31 fastener elements per square centimeter), preferably at least 500 fastener elements per square inch (78 fastener elements per square centimeter).
The array should include, for most tough fastener applications, at least 10 rows of at least 50 fastener elements each.
In many embodiments, the fastener element stems have one or more of the following features: they are of square or rectangular cross-section; they extend perpendicular to the base; and they are integrally molded with the base. In particular, integral molding of the fastener element stems and the base offers several advantages, such as avoiding the need to handle and attach individual stems, and elimination of a stem-base interface.
In many constructions, the fastener element heads have one or more of the following features: they each have upper surfaces that are generally flat over an area covering their respective stems; they each have an overall thickness, measured along their respective stems, of less than about 0.015 inch (0.38 millimeter); and they each have a maximum lateral extent, measured in a direction perpendicular to their respective stems, of between about 0.01 and 0.04 inch (0.25 and 1.0 millimeter).
In some patterns, the fastener element heads each have a lateral extent, measured along their respective rows, greater than a nominal distance between opposing surfaces of adjacent heads within each row.
In some preferred embodiments, the touch fastener has an overall thickness, including a thickness of the sheet-form base and an average height of the fastener elements, of less than about 0.075 inch (1.9 millimeters).
It is preferred that the fastener elements are arranged to have a bulk overlap ratio, when engaged with an identical pattern at a zero degree engagement angle, of less than about 2.0 percent, more preferably about zero percent.
It is also preferred that the fastener elements be constructed and arranged to provide an engagement resistance ratio, when engaged with an identical pattern at a 45 degree engagement angle, of less than about 2.5, more preferably less than about 2.0.
In some cases, the fastener elements are constructed and arranged to provide an engagement resistance ratio, when engaged with an identical pattern at a 90 degree engagement angle, of less than about 1.7, preferably less than about 1.2.
One aspect of the invention features folding such a fastener product over onto itself and engaging two portions of the fastener element array. Another aspect features such a fastener product so folded over and engaged with itself. Yet another aspect features two strips of the above-described product with their respective arrays of fastener elements engaged, such as at a zero degree engagement angle. Such an engaged pair of fastener strips preferably has an overall thickness, when compressed under a light load sufficient to engage the fastener elements of each strip against the base of the other strip, of less than about 0.08 inch (2 millimeters).
According to yet another aspect of the invention, a touch fastener product has a sheet-form base and an array of fastener elements, with each fastener element having a stem extending from a broad side of the base to a distal head overhanging the base and having an upper surface that is generally flat over an area covering its respective stem. The fastener elements are arranged in an ordered pattern of straight rows, with the fastener element heads covering the base at a head density of between about 20 and 35 percent. The fastener elements are arranged to provide a bulk engagement ratio of at least 100 percent when engaged with an identical pattern at a zero degree engagement angle.
In some preferred embodiments, the fastener elements are arranged to define a sufficient number and pattern of pockets between associated groups of adjacent stems to provide a bulk locking ratio of at least 10 percent when engaged with an identical pattern at a zero degree engagement angle.
Preferably, the fastener element stems are integrally molded with and extend perpendicularly from the base.
In many preferred patterns, the fastener elements are arranged in a repeating pattern of row groupings, with each row grouping having a three row band of fastener elements spaced apart from adjacent rows of fastener elements by a distance greater than row spacing within the band. The three row band may consist of two outer rows of laterally aligned fastener elements and a middle row of fastener elements longitudinally offset from adjacent fastener elements of the outer rows, for example.
In some patterns, the fastener elements are arranged in a repeating pattern of four-element clusters, with each cluster consisting of four fastener elements arranged at four corners of a four-sided polygonal area and spaced from adjacent clusters by a distance greater than a greatest side length of the polygonal area.
In some cases, the fastener elements are arranged in a repeating pattern of four-element clusters, with each cluster consisting of four fastener elements arranged at four corners of a four-sided polygonal area, a clearance between a first pair of opposing fastener element heads at opposite corners of the area being greater than a nominal diameter of the fastener element heads, and a clearance between a second pair of opposing fastener element heads at opposite corners of the area being less than the nominal diameter of the fastener element heads.
The fastener elements are preferably arranged to have a bulk overlap ratio, when engaged with an identical pattern at a zero degree engagement angle, of less than about 2.0 percent.
The fastener elements are also preferably constructed and arranged to provide an engagement resistance ratio, when engaged with an identical pattern at a 45 degree engagement angle, of less than about 2.5.
According to another aspect of the invention, a touch fastener product has a sheet-form base and an array of fastener elements, each fastener element having a stem extending from a broad side of the base to a distal head overhanging the base. The fastener elements are arranged in a repeating pattern of row groupings, each row grouping having a three row band of fastener elements spaced apart from adjacent rows of fastener elements by a distance greater than row spacing within the band.
Preferably, the fastener element stems are integrally molded with, and extend perpendicularly from, the base, and the fastener elements are arranged in an ordered pattern of straight rows.
The fastener elements are arranged, in some patterns, to provide a bulk engagement ratio of at least 100 percent when engaged with an identical pattern at a zero degree engagement angle.
In some embodiments, the fastener elements are arranged to define a sufficient number and pattern of pockets between associated groups of adjacent stems to provide a bulk locking ratio of at least 10 percent when engaged with an identical pattern at a zero degree engagement angle.
In some arrangements, the three row band consists of two outer rows of laterally aligned fastener elements and a middle row of fastener elements longitudinally offset from adjacent fastener elements of the outer rows. Preferably, each fastener element of the middle row is equidistant from two adjacent fastener elements of each of the outer rows.
In some configurations, a clearance between opposing surfaces of adjacent fastener element heads along the middle row is less than a nominal lateral extent, measured long the middle row, of the fastener element heads, such that during engagement, at least some of the fastener element stems of the middle row are deflected.
Preferably, particularly in such configurations, a clearance between opposing surfaces of adjacent fastener elements of the outer rows, measured across the three row band, is greater than a nominal lateral extent, measured long the middle row, of the fastener element heads, such that engagement does not require the deflection of both fastener elements of each opposing outer row pair.
In some patterns, each row grouping comprises the three row band and at least one single row band of fastener elements. For example, in one case, each row group consists of the three row band and a single row band of fastener elements spaced midway between the three row band of the grouping and a three row band of an adjacent grouping. In another illustrated pattern, each row group consists of the three row band and two single row bands of fastener elements separated by a distance greater than the row spacing within the three row band.
Preferably, the fastener element heads cover the base at a head density of between 20 and 35 percent, and the array has an overall fastener element density of at least 200 fastener elements per square inch (31 fastener elements per square centimeter).
According to another aspect of the invention, a touch fastener product includes a sheet-form base and an array of fastener elements each having a stem extending from a broad side of the base to a distal head overhanging the base, with the fastener elements arranged in an ordered pattern of straight rows. Notably, the fastener elements are constructed and arranged to provide an engagement resistance ratio, when engaged with an identical pattern at a 45 degree engagement angle, of less than about 2.5 (preferably, less than about 2.0).
In some embodiments, the fastener elements are constructed and arranged to provide an engagement resistance ratio, when engaged with an identical pattern at a 90 degree engagement angle, of less than about 1.8 (preferably, less than about 1.2).
By proper patterning, engagement and performance properties of self-engageable fastener element arrays can be enhanced, while maintaining a high degree of pattern order that lends itself to various manufacturing processes and tooling. In many cases, this can even be accomplished with fastener elements aligned in straight rows. Many of these patterns and fastener element constructions are also useful for engaging loops or fibers of a female fastener.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.